Memory cells, semiconductor device structures, systems including such cells, and methods of fabrication

ABSTRACT

Memory cells including cell cores having free regions are disclosed. The free regions exhibit a strain that affects a magnetization orientation within the cell core. A stressor structure may exert a stress upon at least a portion of the cell core to effect the strain state of the free region. Also disclosed are semiconductor device structures and systems including such memory cells as well as methods for forming such memory cells.

FIELD

The present disclosure, in various embodiments, relates generally to thefield of memory device design and fabrication. More particularly, thepresent disclosure relates to design and fabrication of memory cellscharacterized as Spin Torque Transfer Magnetic Random Access Memory(STT-MRAM).

BACKGROUND

Magnetic Random Access Memory (MRAM) is a non-volatile computer memorytechnology based on magnetoresistance. MRAM is non-volatile and so canmaintain memory content when the memory device is not powered. MRAM datais stored by magnetoresistive elements. Generally, the magnetoresistiveelements in an MRAM cell are made from two magnetic regions, each ofwhich accepts and sustains magnetization. The magnetization of oneregion (the “pinned region”) is fixed in its magnetic orientation, andthe magnetization orientation of the other region (the “free region”)can be changed. Thus, a programming current can cause the magneticorientations of the two magnetic regions to be either parallel, giving alower electrical resistance across the magnetoresistive elements (whichmay be defined as a “0” state), or antiparallel, giving a higherelectrical resistance across the magnetoresistive elements (which may bedefined as a “1” state) of the MRAM cell. The switching of the magneticorientation of the free region and the resulting high or low resistancestates across the magnetoresistive elements provide for the write andread operations of the typical MRAM cell.

One type of MRAM cell is a spin torque transfer MRAM (STT-MRAM) cell. Aconventional STT-MRAM cell may include a magnetic cell core, which mayinclude a magnetic tunnel junction (MTJ) or a spin valve structure. AnMTJ is a magnetoresistive data storing element including two magneticregions (one pinned and one free) and a non-magnetic, electricallyinsulating region in between, which may be accessed through data lines(e.g., bit lines), access lines (e.g., word lines), and an accesstransistor. A spin valve has a structure similar to the MTJ, except aspin valve has a conductive region in between the two magnetic regions.

In operation, a programming current may flow through the accesstransistor and the magnetic cell core. The pinned region within the cellcore polarizes the electron spin of the programming current, and torqueis created as the spin-polarized current passes through the core. Thespin-polarized electron current interacts with the free region byexerting a torque on the free region. When the torque of thespin-polarized electron current passing through the core is greater thana critical switching current density (J_(c)) of the free region, thetorque exerted by the spin-polarized electron current is sufficient toswitch the direction of the magnetization of the free region. Thus, theprogramming current can be used to cause the magnetization of the freeregion to be aligned either parallel to or antiparallel to themagnetization of the pinned region, and, when the magnetization of thefree region is switched between parallel and antiparallel, theresistance state across the core is changed.

The free regions and pinned regions of conventional STT-MRAM cellsexhibit magnetization orientations that are horizontal, also known as“in-plane,” with the width of the regions. Accordingly, themagnetization orientations are parallel (or antiparallel) to a planedefined by a primary surface of a substrate supporting the STT-MRAMcell. These wide, in-plane STT-MRAM cells have large footprints, makingscaling of the cells below twenty-five nanometers a challenge.

Perpendicularly oriented STT-MRAM cells may require smaller cell widthsthan in-plane STT-MRAM cells, accommodating greater cell packing. Also,the associated perpendicular magnetizations (also known in the art asperpendicular magnetic anisotropy (“PMA”)) of perpendicularly orientedSTT-MRAM cells may have greatly reduced required switching voltagecompared to an in-plane STT-MRAM cell. Therefore, efforts have been madeto faun perpendicularly oriented (“out-of-plane”) STT-MRAM cells inwhich the pinned regions and the free regions exhibit verticalmagnetization orientations. However, finding and implementing suitablematerials and designs for the cell core to achieve the verticalmagnetization orientations has been a challenge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a portion of a memory array havingmemory cells fabricated according to an embodiment of the presentdisclosure;

FIGS. 2A through 2F are cross-sectional, elevation, schematicillustrations of STT-MRAM cells according to embodiments of the presentdisclosure;

FIGS. 3A through 3F are cross-sectional, plan, schematic illustrationsof the STT-MRAM cells of FIGS. 2A through 2F, respectively, taken alongsection lines A-A, B-B, C-C, D-D, E-E, and F-F, respectively, accordingto embodiments of the present disclosure;

FIGS. 4A through 4F are cross-sectional, plan, schematic illustrationsof the STT-MRAM cells of FIGS. 2A through 2F, respectively, taken alongsection lines A-A, B-B, C-C, D-D, E-E, and F-F, respectively, accordingto embodiments of the present disclosure;

FIGS. 5A through 5C are cross-sectional, elevation, schematicillustrations of a free region during various stages of application oflateral compressive stress according to an embodiment of the presentdisclosure;

FIGS. 6A through 6C are cross-sectional, elevation, schematicillustrations of a free region during various stages of application ofvertical tensile stress according to an embodiment of the presentdisclosure;

FIG. 7 is a simplified block diagram of a semiconductor device includingmemory cells of an embodiment of the present disclosure; and

FIG. 8 is a simplified block diagram of a system implemented accordingto one or more embodiments described herein.

DETAILED DESCRIPTION

Memory cells, semiconductor device structures including such memorycells, systems including arrays of such memory cells, and methods offorming such memory cells are disclosed. The memory cells include cellcores that have a free region exhibiting strain effecting a verticalmagnetization orientation. Thus, the vertical magnetization orientationof the strained free region of the memory cell is influenced by theapplied stress. The applied stress may be a mechanical stress, a thermalstress, or both. The applied stress and the effected verticalmagnetization orientation exhibited by the free region may be permanentor temporary.

As used herein, the term “substrate” means and includes a base materialor construction upon which components, such as those within memorycells, are formed. The substrate may be a semiconductor substrate, abase semiconductor material on a supporting structure, a metalelectrode, or a semiconductor substrate having one or more materials,structures, or regions formed thereon. The substrate may be aconventional silicon substrate or other bulk substrate including asemiconductive material. As used herein, the term “bulk substrate” meansand includes not only silicon wafers, but also silicon-on-insulator(“SOI”) substrates, such as silicon-on-sapphire (“SOS”) substrates orsilicon-on-glass (“SOG”) substrates, epitaxial layers of silicon on abase semiconductor foundation, or other semiconductor or optoelectronicmaterials, such as silicon-germanium (Si_(1-x)Ge_(x), where x is, forexample, a mole fraction between 0.2 and 0.8), germanium (Ge), galliumarsenide (GaAs), gallium nitride (GaN), or indium phosphide (InP), amongothers. Furthermore, when reference is made to a “substrate” in thefollowing description, previous process stages may have been utilized toform materials, regions, or junctions in the base semiconductorstructure or foundation.

As used herein, the term STT-MRAM cell means and includes a magneticcell structure that may include an MTJ, as discussed above, if anon-magnetic region, disposed between the free region and the pinnedregion, is insulative. Alternatively, the magnetic cell structure of theSTT-MRAM cell may include a spin valve, if the non-magnetic region,disposed between the free region and the pinned region, is conductive.

As used herein, the term “pinned region” means and includes a region ofmagnetic material within the STT-MRAM cell that has a fixedmagnetization orientation during use and operation of the STT-MRAM cell.The fixed magnetization orientation of the pinned region may beinfluenced by an externally applied stress, which may be applied by astressor structure, such that the pinned region may exhibit a strain.The magnetization orientation exhibited by the strained pinned regionmay be different, due to the application of the stress upon the pinnedregion, than it would be without application of the stress.Alternatively, the magnetization orientation exhibited by the pinnedregion may be uninfluenced by an applied stress, such that themagnetization exhibited by the strained pinned region would be the sameregardless as a magnetization exhibited by a non-strained pinned region.The magnetization orientation of the pinned region of the presentdisclosure may exhibit a vertical magnetization orientation.

As used herein, the term “free region” means and includes a region ofmagnetic material within the STT-MRAM cell that has a switchablemagnetization orientation during use and operation of the STT-MRAM cell.The magnetization orientation may be switched between a “parallel”direction, in which the magnetization orientation exhibited by the freeregion and the magnetization orientation exhibited by the pinned regionare directed in the same direction, to an “antiparallel” direction, inwhich the magnetization orientation exhibited by the free region and themagnetization orientation exhibited by the pinned region are directed inopposite directions.

As used herein, the term “cell core” means and includes a memory cellstructure comprising the free region and pinned region and throughwhich, during operation of the memory cell, current flows to effect aparallel or antiparallel magnetic orientation within the free region.

As used herein, the term “vertical” means and includes a direction thatis perpendicular to the width of the respective region. “Vertical” mayalso mean and include a direction that is perpendicular to a primarysurface of a substrate supporting the STT-MRAM cell.

As used herein, the terms “first,” “second,” “third,” etc., may describevarious elements, components, regions, materials, and/or sections, noneof which are limited by these terms. These terms are used only todistinguish one element, component, region, material, or section fromanother element, component, region, material, or section. Thus, “a firstelement,” “a first component,” “a first region,” “a first material,” or“a first section” discussed below could be termed a second element, asecond component, a second region, a second material, or second sectionwithout departing from the teachings herein.

As used herein, spatially relative terms, such as “beneath,” “below,”“lower,” “bottom,” “above,” “upper,” “top,” “front,” “rear,” “left,”“right,” and the like, may be used for ease of description to describeone element's or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. Unless otherwise specified,the spatially relative terms are intended to encompass differentorientations of the materials in addition to the orientation depicted inthe figures. For example, if materials in the figures are inverted,elements described as “below” or “beneath” or “under” or “on bottom of”other elements or features would then be oriented “above” or “on top of”the other elements or features. Thus, the term “below” can encompassboth an orientation of above and below, depending on the context inwhich the term is used, which will be evident to one of ordinary skillin the art. The materials may be otherwise oriented (rotated 90 degrees,inverted, etc.) and the spatially relative descriptors used hereininterpreted accordingly.

As used herein, reference to an element as being “on” or “over” anotherelement means and includes the element being directly on top of,adjacent to, underneath, or in direct contact with the other element. Italso includes the element being indirectly on top of, adjacent to,underneath, or near the other element, with other elements presenttherebetween. In contrast, when an element is referred to as being“directly on” another element, there are no intervening elementspresent.

As used herein, the terms “comprises,” “comprising,” “includes,” and/or“including” specify the presence of stated features, regions, integers,stages, operations, elements, materials, components, and/or groups, butdo not preclude the presence or addition of one or more other features,regions, integers, stages, operations, elements, materials, components,and/or groups thereof.

As used herein, “and/or” includes any and all combinations of one ormore of the associated listed items.

As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise.

The illustrations presented herein are not meant to be actual views ofany particular material, component, structure, device, or system, butare merely idealized representations that are employed to describeembodiments of the present disclosure.

Embodiments are described herein with reference to the illustrations.Variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, embodiments described herein are not to be construed asbeing limited to the particular shapes or regions as illustrated butinclude deviations in shapes that result, for example, frommanufacturing. For example, a region illustrated or described asbox-shaped may have rough and/or nonlinear features. Moreover, sharpangles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and do notlimit the scope of the present claims.

The following description provides specific details, such as materialtypes and processing conditions, in order to provide a thoroughdescription of embodiments of the disclosed devices and methods.However, a person of ordinary skill in the art will understand that theembodiments of the devices and methods may be practiced withoutemploying these specific details. Indeed, the embodiments of the devicesand methods may be practiced in conjunction with conventionalsemiconductor fabrication techniques employed in the industry.

The fabrication processes described herein do not form a completeprocess flow for processing semiconductor device structures. Theremainder of the process flow is known to those of ordinary skill in theart. Accordingly, only the methods and semiconductor device structuresnecessary to understand embodiments of the present devices and methodsare described herein.

Unless the context indicates otherwise, the materials described hereinmay be formed by any conventional technique including, but not limitedto, spin coating, blanket coating, chemical vapor deposition (“CVD”),plasma enhanced CVD, atomic layer deposition (“ALD”), plasma enhancedALD, or physical vapor deposition (“PVD”). Alternatively, the materialsmay be grown in situ. Depending on the specific material to be formed,the technique for depositing or growing the material may be selected bya person of ordinary skill in the art.

Reference will now be made to the drawings, where like numerals refer tolike components throughout. The drawings are not necessarily to scale.

A memory cell is disclosed. The memory cell includes a magnetic cellcore having a free region exhibiting strain. The strain effects avertical magnetization orientation.

FIG. 1 illustrates an STT-MRAM system 80 that includes periphery devices90 in operable communication with an STT-MRAM cell 100, a plurality ofwhich may be fabricated to form an array of memory cells in a gridpattern including a number of rows and columns, or in various otherarrangements, depending on the system requirements and fabricationtechnology. The STT-MRAM cell 100 includes a cell core 110, an accesstransistor 130, a conductive material that may function as a bit line140, a conductive material that may function as a word line 150, and aconductive material that may function as a source line 160. Theperiphery devices 90 of the STT-MRAM system 80 may include read/writecircuitry 170, a bit line reference 180, and a sense amplifier 190. Thecell core 110 may include a magnetic tunnel junction (MTJ), including afree region and a pinned region. The STT-MRAM cell 100 may also includeat least one stressor structure 120, which is external to the cell core110. As used herein, a structure “external” to another structure mayinclude a structure that is physically isolated from the anotherstructure, a structure that is electrically isolated from the anotherstructure, a structure that is not in electrical communication with theanother structure, a structure that is not positioned vertically betweenthe uppermost region of the cell core 110 that is in electricalcommunication with the bit line 140 and the lowermost region of the cellcore 110 that is in electrical communication with the word line 150, ora combination thereof.

In use and operation, when the STT-MRAM cell 100 is selected to beprogrammed, a programming current is applied to the STT-MRAM cell 100,and the current is spin-polarized by the pinned region and exerts atorque on the free region, which switches the magnetization of the freeregion to “write to” or “program” the STT-MRAM cell 100. In a readoperation of the STT-MRAM cell 100, a current is used to detect theresistance state of the cell core 110. The stressor structure 120 mayexert a stress upon at least a portion of the cell core 110. Due to theapplication of the stress, a free region within the cell core 110 mayexhibit a strain effecting a vertically oriented magnetization exhibitedby the free region within the cell core 110, which vertical orientationmay decrease the critical switching current required to switch themagnetization of the free region, thus allowing a smaller programmingcurrent to write the STT-MRAM cell 100. The vertical magnetizationorientation may further allow for use of a cell core 110 with a smallerlateral dimension, thus allowing for improved scalability and devicedensity.

As previously discussed, a programming current is applied for the writeoperation of the STT-MRAM cell 100. To initiate the programming current,the read/write circuitry 170 may generate a write current to the bitline 140 and the source line 160. The polarity of the voltage betweenthe bit line 140 and the source line 160 determines the switch inmagnetization of the free region in the cell core 110. Once the freeregion is magnetized according to the spin polarity of the programmingcurrent, the programmed state is written to the STT-MRAM cell 100.

To read the STT-MRAM cell 100, the read/write circuitry 170 generates aread current to the bit line 140 and the source line 160 through thecell core 110 and the access transistor 130. The programmed state of theSTT-MRAM cell 100 relates to the resistance across the cell core 110,which may be determined by the voltage difference between the bit line140 and the source line 160. In some embodiments, the voltage differencemay be compared to the bit line reference 180 and amplified by the senseamplifier 190.

FIG. 2A illustrates a plurality of STT-MRAM cells 100 according to anembodiment of the present disclosure. Each STT-MRAM cell 100 includes acell core 110 supported by a substrate 10. The cell core 110 includes afree region 112 and a pinned region 114. A non-magnetic region 113,which may be conductive or insulative, is disposed between the freeregion 112 and the pinned region 114. The cell core 110 forms an MTJ ifthe non-magnetic region 113 is insulative, or forms a spin valve if thenon-magnetic region 113 is conductive. In embodiments in which the cellcore 110 forms an MTJ, the non-magnetic region 113 between the freeregion 112 and the pinned region 114 may serve as an insulator betweenthe two regions 112, 114. The non-magnetic region 113 may be formed fromor comprise Al_(x)O_(y), MgO, AlN, SiN, CaO_(x), NiO_(x), Hf_(x)O_(y),Ta_(x)O_(y), Zr_(x)O_(y), NiMnO_(x), Mg_(x)F_(y), SiC, SiO₂,SiO_(x)N_(y), or any combination of the above materials.

The free region 112 and pinned region 114 may be formed from or compriseferromagnetic materials, such as Co, Fe, Ni or its alloys, NiFe, CoFe,CoNiFe, or doped alloys CoX, CoFeX, CoNiFeX (X═B, Cu, Re, Ru, Rh, Hf,Pd, Pt, C), or other half-metallic ferromagnetic material such as NiMnSband PtMnSb, for example. More particularly, for example, the free region112 may be formed from or comprise one or more of a material exhibitingmagnetostriction (e.g., without limitation, Co_(x)Fe_(y)B_(z)), amaterial exhibiting an L1₀ crystal structure, a material exhibiting auniaxial magnetic anisotropy, and a Heusler alloy, which characteristicsare not mutually exclusive. Alternatively or additionally, in someembodiments, the free region 112 may be formed from or comprise layeredmaterials. For example, and without limitation, the free region 112 maybe formed from or comprise repeating layers of cobalt and platinum, witha layer of platinum disposed between layers of cobalt and vice versa. Asanother example, without limitation, the free region 112 may compriserepeating layers of cobalt and nickel, with a layer of nickel disposedbetween layers of cobalt and vice versa.

The pinned region 114 is so named because it has a fixed magnetizationwith a fixed or pinned preferred orientation, which is represented bythe unidirectional arrow illustrated in the pinned region 114 of FIGS.2A through 2F. The bidirectional arrow illustrated in the free region112 represents that the free region 112 may be magnetized either in adirection parallel to the orientation of the pinned region 114, whichgives a low resistance, or in a direction antiparallel to theorientation of the pinned region 114, which gives a high resistance.

The cell core 110 may optionally also include other regions in additionto the free region 112, non-magnetic region 113, and pinned region 114.For example, as illustrated in FIG. 2A, the cell core 110 may include anantiferromagnetic region 115, which may be situated below the pinnedregion 114 to achieve the pinning through exchange coupling. Additionalnon-magnetic regions may be included in the cell core 110. For example,another non-magnetic region 111 may be situated over the free region112. Other regions within the cell core 110 may include any ofpiezoelectric regions, additional free regions, additional pinnedregions, additional antiferromagnetic regions, or other regions of knownSTT-MRAM cells.

External to the cell core 110, at least one stressor structure 120 maybe present. The stressor structure 120 exerts a stress, either directlyor indirectly, upon the free region 112. The exerted stress may be due,at least in part, to the configuration and positioning of the stressorstructure 120 relative to the free region 112. The stressor structure120 may, directly or indirectly, exert a stress upon at least a portionof the cell core 110 to thereby effect a strain exhibited by the freeregion 112. The strained state of the free region 112 effects a verticalmagnetization orientation in the free region 112. Accordingly, thestress exerted by the stressor structure 120 causes the strain exhibitedby the free region 112, which effects the vertical magnetizationorientation of the free region 112.

The stressor structure 120 may be formed of or comprise one or morestressor materials. Such stressor materials may include, for example andwithout limitation, SiO or Si₃N₄. In other embodiments, the stressormaterial may include, for example and without limitation, a spin-onglass material formulated to shrink substantially upon annealing. Instill other embodiments, the stressor material may include, for exampleand without limitation, an amorphous material formulated to densify uponannealing.

The stressor structure 120 exerts a stress upon a neighboring materialor structure, such as upon at least one region of the cell core 110 oran insulative material disposed between the stressor structure 120 andat least one region of the cell core 110. The stressor structure 120 maybe configured and positioned to apply either a compressive stress or atensile stress to a neighboring material. Additionally, the stressorstructure 120 may be configured and positioned to exert an essentiallylateral stress or an essentially vertical stress upon a neighboringmaterial. As used herein, a “lateral stress” is a stress directed in adirection parallel with the width of the structure upon which thelateral stress is exerted. A lateral stress may be directed in adirection that is parallel with a plane defined by the primary surfaceof a substrate supporting the STT-MRAM cell in which the structure, uponwhich the lateral stress is exerted, is supported. Also, as used herein,a “vertical stress” is a stress directed in a direction parallel withthe height of the structure upon which the vertical stress is exerted. Avertical stress may be directed in a direction that is perpendicularwith the plane defined by the primary surface of the substratesupporting the STT-MRAM cell in which the structure, upon which thevertical stress is exerted, is supported.

In other embodiments, the stressor structure 120 may be configured andpositioned to exert an angled stress upon the neighboring material.Therefore, the stressor structure 120 may exert a lateral compressivestress, a lateral tensile stress, a vertical compressive stress, avertical tensile stress, an angled compressive stress, or an angledtensile stress upon at least one neighboring material, which neighboringmaterial may be the free region 112 of the cell core 110 or anothermaterial disposed between the stressor structure 120 and the free region112 of the cell core 110. It is contemplated that the materialcomprising the stressor structure 120 be selected so as to exert,following formation of the stressor structure 120, the desired amount ofstress of the desired type (e.g., compressive or tensile), in thedesired direction (e.g., lateral, vertical, or angled) on theneighboring material so as to exhibit the desired strain by the freeregion 112 and to effect a vertical magnetization orientation within thestrained free region 112 of the cell core 110.

As illustrated in FIG. 2A, the STT-MRAM cell 100 may include more thanone stressor structure 120. For example, as shown, the STT-MRAM cell 100may include a laterally-adjacent stressor structure 120L and avertically-adjacent stressor structure 120V. Such laterally-adjacentstressor structure 120L within the STT-MRAM cell 100 may be situatedsuch that the cell core 110 is disposed laterally between at least twosegments of the laterally-adjacent stressor structure 120L. Suchlaterally-adjacent segments of the laterally-adjacent stressor structure120L may be configured and positioned to exert, either directly orindirectly, a lateral stress, either compressive or tensile, upon atleast the free region 112 of the cell core 110.

The vertically-adjacent stressor structure 120V may be disposed above orbelow the cell core 110, or may be disposed both above and below thecell core 110, as shown in FIG. 2A. Such vertically-adjacent stressorstructures 120V may be configured and positioned to exert, eitherdirectly or indirectly, a vertical stress, either compressive ortensile, upon at least the free region 112 of the cell core 110.

The word line 150 of each STT-MRAM cell 100 may be formed in andsupported by the substrate 10. The bit line 140 and word line 150 may bedisposed between the cell core 110 and a vertically-adjacent stressorstructure 120V, as shown in FIG. 2A, and the conductive material formingthe bit line 140 and the word line 150 may be in operable communicationwith the cell core 110. In such embodiments, the vertically-adjacentstressor structures 120V may be configured and positioned to exert thevertical stress more directly upon each or either of the bit line 140and the word line 150 before such vertical stress is indirectly exertedupon the free region 112 of the cell core 110.

In other embodiments (not shown), a vertically-adjacent stressorstructure 120V may be disposed, additionally or alternatively, betweenthe bit line 140 and the cell core 110, such as between the bit line 140and the non-magnetic region 111. Likewise, such embodiments may also oralternatively include a vertically-adjacent stressor structure 120Vdisposed between the word line 150 and the cell core 110, such asbetween the word line 150 and the antiferromagnetic region 115.

The stressor structure 120 may be physically or electrically isolated,or both physically and electrically isolated, from the cell core 110.For example, an insulative material 20 may isolate the stressorstructure 120 from the cell core 110. The insulative material 20 may beformed from or comprise known interlayer dielectric materials, such as,for example and without limitation, silicon dioxide.

The laterally-adjacent segments of the stressor structure 120L mayextend all or only a portion of a height defined by the cell core 110.For example, as shown in FIG. 2A, the laterally-adjacent segments oflaterally-adjacent stressor structure 120L may extend all of a heightdefined by the free region 112, non-magnetic region 113, and pinnedregion 114 of the cell core 110 but may not physically contact or extendbetween the bit line 140 and word line 150.

The laterally-adjacent segments of the at least one laterally-adjacentstressor structure 120L may define a width that is less than or equal toa width defined by the wider of the bit line 140 and the word line 150.In such embodiments, therefore, the width of the wider of the bit line140 and the word line 150 may define the width of the STT-MRAM cell 100.

With reference to FIG. 2B, in some embodiments, the stressor structure120 of the STT-MRAM cell 100 may not be physically isolated from thecell core 110. In such embodiments, the laterally-adjacent stressorstructure 120L may be formed directly on the cell core 110, such asbeing formed on sidewalls defined by the cell core 110. Suchlaterally-adjacent stressor structure 120L may be in direct physicalcontact with one or more of the free region 112, the bit line 140, andthe word line 150.

Also, as shown in FIG. 2B, in some embodiments, the laterally-adjacentstressor structure 120L may extend the height of the cell core 110. Thelaterally-adjacent stressor structure 120L may also span a distancebetween neighboring cell cores 110, rather than defining discretesegments of laterally-adjacent stressor structure 120L betweenneighboring cell cores 110.

With reference to FIG. 2C, in some embodiments, the laterally-adjacentstressor structure 120L may extend essentially the height of the cellcore 110 while being physically and electrically isolated from the cellcore 110 by insulative material 20.

With reference to FIG. 2D, in some embodiments, the laterally-adjacentstressor structure 120L may extend essentially only the height of thefree region 112 of the cell core 110. Such laterally-adjacent stressorstructures 120L may essentially span between free regions 112 ofneighboring cell cores 110 while being physically and electricallyisolated from the cell core 110 by insulative material 20.

With reference to FIG. 2E, in some embodiments, the laterally-adjacentstressor structure 120L includes more than one stressor material. Suchlaterally-adjacent stressor structures 120L may include a first stressormaterial 122 proximate to the cell core 110 with a second stressormaterial 124 proximate to the first stressor material 122, the firststressor material 122 being disposed between the cell core 110 and thesecond stressor material 124. In other embodiments, more than twostressor materials may be included in the laterally-adjacent stressorstructure 120L. Though the laterally-adjacent stressor structure 120L isillustrated as being in physical contact with the cell core 110, inother embodiments (not shown), the laterally-adjacent stressor structure120L of more than one stressor material may be electrically isolated,physically isolated, or both electrically and physically isolated fromthe cell core 110. Likewise, though the laterally-adjacent stressorstructure 120L is illustrated as extending the height of the cell core110, in other embodiments (not shown), the laterally-adjacent stressorstructure 120L of more than one stressor material may extend only aportion of the height of the cell core 110, e.g., extending only alongthe height of the free region 112 of the cell core 110.

With reference to FIG. 2F, in some embodiments, the laterally-adjacentstressor structure 120L may be directly adjacent and in contact with thecell core 110, while not spanning between neighboring cell cores 110.

In other embodiments (not shown), the STT-MRAM cell 100 may includevertically-adjacent stressor structures 120V (e.g., FIG. 2A) of one ormore materials in addition to the laterally-adjacent stressor structures120L illustrated in FIGS. 2B-2F. In such embodiments, thevertically-adjacent stressor structures 120V may form discreteindividual vertically-adjacent stressor structures 120V relative to itsrespective STT-MRAM cell 100. In other such embodiments, thevertically-adjacent stressor structures 120V may be continuous over andbetween a plurality of STT-MRAM cells 100. In still other suchembodiments, the vertically-adjacent stressor structures 120V may beformed of more than one material in a mixture or film structure.

In some embodiments, the cell core 110 may be essentially cylindricallyshaped. In such embodiments, a laterally-adjacent stressor structure120L may surround the cell core 110, and the cell core 110 may becentrally disposed within the laterally-adjacent stressor structure120L. For example, FIGS. 3A through 3F illustrate a cross-sectional viewtaken along section lines A-A of FIG. 2A, B-B of FIG. 2B, C-C of FIG.2C, D-D of FIG. 2D, E-E of FIG. 2E, and F-F of FIG. 2F, respectively.

In other embodiments, the cell core 110 may be essentially box shaped.In such embodiments, a laterally-adjacent stressor structure 120L maysurround the cell core 110, and the cell core 110 may be centrallydisposed within the laterally-adjacent stressor structure 120L. Forexample, FIGS. 4A through 4F illustrate a cross-sectional view takenalong section lines A-A of FIG. 2A, B-B of FIG. 2B, C-C of FIG. 2C, D-Dof FIG. 2D, E-E of FIG. 2E, and F-F of FIG. 2F, respectively.

In other embodiments (not shown), a laterally-adjacent stressorstructure 120L is formed in discrete segments such that thelaterally-adjacent stressor structure 120L does not completely laterallysurround the cell core 110. In such embodiments, segments of thelaterally-adjacent stressor structure 120L may be laterally adjacent toonly one or some, but not all, sides of the cell core 110, such as,laterally adjacent to a pair of sides of the cell core 110, as forexample, shown in FIG. 1.

Further disclosed is a method of forming a memory cell. The methodincludes forming a cell core and applying a stress to the cell core toaffect a magnetization orientation exhibited by a material within thecell core.

Forming the memory cell may include forming a cell core including a freeregion 112 and forming a stressor structure 120 isolated from the freeregion 112 by insulative material 20. The cell core with free region 112may be formed using conventional methods, which are not described indetail herein. Likewise, insulative material 20 may be formed onsidewalls of the free region 112 using conventional methods. Thelaterally-adjacent stressor structure 120L may be formed on sidewalls ofeither the free region 112, in embodiments in which no insulativematerial 20 isolates the laterally-adjacent stressor structure 120L andthe free region 112, or may be formed on the insulative material 20. Thestressor structure 120 may be formed by conventional techniques, such asplasma-enhanced CVD, under parameters (e.g., flow rates, temperatures,pressures, concentrations, exposure times) appropriate to form astressor structure 120 exerting stress upon at least one neighboringmaterial, which such neighboring material may be the free region 112 orthe insulative material 20, for example. The stress exerted by thestressor structure 120 may be due to thermal mismatch during temperaturechanges in the fabrication process, due to volume expansion andshrinkage (e.g., due to a differing coefficient of thermal expansionbetween the stressor material comprising the stressor structure 120 anda coefficient of thermal expansion of the neighboring material), or dueto lattice mismatch stress due to material compositions and impuritieswithin the material comprising the stressor structure 120, or anycombination thereof. In other embodiments, such as those in which thestressor structure 120 includes a spin-on glass material formulated toshrink upon annealing, the stress exerted by the stressor structure 120may be generated upon the shrinkage of the stressor material. In stillother embodiments, such as those in which the stressor structure 120includes an amorphous material formulated to densify upon annealing, thestress exerted by the stressor structure 120 may be generated due to thedensification of the stressor material.

With reference to FIGS. 5A-5C, for example, forming a memory cellincluding a cell core with laterally-adjacent stressor structure 120Lmay include forming the cell core 110 (FIGS. 2A-2F) with a free region112′, and, at initial formation, the free region 112′ may not exhibit astrain. Insulative material 20 may be formed on sidewalls of the cellcore 110, and the laterally-adjacent stressor structure 120L may beformed on the insulative material 20. In other embodiments, thelaterally-adjacent stressor structure 120L may be formed directly on thecell core 110. The free region 112′ and laterally-adjacent stressorstructure 120L may, along with other materials of the memory cell, beformed at processing temperatures in excess of room and operatingtemperatures. At such processing temperatures, the laterally-adjacentstressor structure 120L may exhibit physical properties, such as alattice structure, that may change as the laterally-adjacent stressorstructure 120L, and other materials within the STT-MRAM cell 100 (FIGS.2A-2F), cool to room or operating temperatures. For example, at initialformation, illustrated in FIG. 5A, the laterally-adjacent stressorstructure 120L may define a first structure. As the laterally-adjacentstressor structure 120L cools, as illustrated in FIG. 5B, thelaterally-adjacent stressor structure 120L may expand at a greater ratethan a neighboring material, e.g., insulative material 20, and thereforemay intrude upon space previously occupied by the neighboring materialand thereby exert a compressive stress upon the free region 112″,causing the free region 112″ to exhibit an amount of strain. Thismismatch in expansion exerts a lateral compressive stress 500 upon theneighboring material, which strained material may thereafter carryforward the exerted stress by exerting at least a fraction of thelateral compressive stress 500 to its neighboring materials, which mayinclude the free region 112″ of the cell core 110 (FIGS. 2A-2F).Expansion may continue to a maximum expansion, as illustrated in FIG.5C, which may be exhibited when the laterally-adjacent stressorstructure 120L and other materials within the STT-MRAM cell 100 (FIGS.2A-2F) have cooled to room or operating temperatures. Thelaterally-adjacent stressor structure 120L, the resulting lateral stress500, and the state of strain of the free region 112 may remainessentially unchanged following completion of formation and cooling ofthe laterally-adjacent stressor structure 120L and neighboring materialsas they are during use and operation of the STT-MRAM cell 100 (FIGS.2A-2F).

As also illustrated in FIGS. 5A-5C, the non-strained free region 112′,upon initial formation, illustrated in FIG. 5A, may exhibit amagnetization orientation 200 that may be essentially horizontallydisposed. The free region 112′ may continue to exhibit suchhorizontally-oriented magnetization orientation 200 in the absence of astate of strain caused by stress exerted on the free region 112′.However, as illustrated in FIG. 5B, as the lateral compressive stress500 is exerted on the free region 112″ by the laterally-adjacentstressor structure 120L and the free region 112″ takes on a strainedstate, the magnetization orientation 200 may be altered to a morevertical orientation compared to the magnetization orientation 200exhibited by the free region 112′ (FIG. 5A) at initial formation and notin a strained state. At the completion of the formation of the freeregion 112 and the laterally-adjacent stressor structure 120L, asillustrated in FIG. 5C, the free region 112, now in a state of strain,may exhibit an essentially vertical magnetization orientation 200.

Though FIG. 5C illustrates an essentially vertical magnetizationorientation 200 with upwardly-pointed arrows, the represented upwarddirection may represent the magnetization direction exhibited by thestrained free region 112 either when in parallel or when antiparallelwith the magnetization direction exhibited by the pinned region 114(FIGS. 2A-2F). Due to the parallel-to-antiparallel switching of the freeregion 112, an induced vertical magnetization orientation 200 within thefree region 112, due to a lateral compressive stress, may,alternatively, be represented by a downwardly-pointed arrow. Further,because the direction of the magnetization orientation 200 exhibited bya strained free region 112 under a lateral compressive stress 500 maydepend on the material or materials comprising the free region 112, itshould be understood that the present disclosure is not limited toachieving a vertical magnetization orientation within the strained freeregion 112 via a lateral stress that is compressive. In otherembodiments, the material comprising the free region 112 may be suchthat exerting a lateral tensile stress, directly or indirectly, upon thefree region 112 may exhibit the strain that affects the magnetizationorientation within the free region 112 so as to achieve the desiredvertical magnetization orientation therein. In such embodiments,therefore, the composition of the laterally-adjacent stressor structure120L and the technique for forming the laterally-adjacent stressorstructure 120L may be tuned to achieve a laterally-adjacent stressorstructure 120L configured to exert the lateral tensile stress, directlyor indirectly, upon the free region 112.

With reference to FIGS. 6A-6C, illustrated is another embodiment. Amethod of forming the memory cell according to this embodiment includesforming a first vertically-adjacent stressor structure 120V′, formingthe cell core 110 above the first vertically-adjacent stressor structure120V′, and forming a second vertically-adjacent stressor structure 120V″above the cell core 110. The stressor material or materials comprisingthe vertically-adjacent stressor structures 120V′, 120V″ may beformulated such that, as a result of fabrication or other treatment, thematerial contracts away from neighboring materials, exerting a verticaltensile stress indirectly upon the free region 112, which is in a stateof strain. Accordingly, at initial formation, the free region 112′, notin a strained state, may exhibit an essentially horizontal magnetizationorientation 200, as illustrated in FIG. 6A. As the vertically-adjacentstressor structures 120V′, 120V″ contract, as, for example, duringcooling, the vertically-adjacent stressor structures 120V′, 120V″ exerta vertical tensile stress 600 upon neighboring materials, and therefore,indirectly exerts a vertical tensile stress 600 upon the free region112″, altering the direction of the magnetization orientation 200 of thesomewhat-strained free region 112″, as illustrated in FIG. 6B. Aftercompletion of fabrication, the vertically-adjacent stressor structures120V′, 120V″ continues to exert a vertical tensile stress 600 upon thefree region 112 such that the strained free region 112 exhibits anessentially vertical magnetization orientation 200, as illustrated inFIG. 6C. The contraction of the vertically-adjacent stressor structures120V′, 120V″ and the resulting vertical stress 600 may be essentiallyunchanging following completion of formation and cooling of thevertically-adjacent stressor structures 120V′, 120V″ and neighboringmaterials.

Again, though FIG. 6C illustrates an essentially vertical magnetizationorientation 200 with upwardly-pointed arrows, the represented upwarddirection may represent the magnetization direction exhibited by thestrained free region 112 either when in parallel or when antiparallelwith the magnetization direction exhibited by the pinned region 114(FIGS. 2A-2F). An induced vertical magnetization orientation 200 withinthe strained free region 112 due to a vertical tensile stress may,alternatively, be represented by a downwardly-pointed arrow (notdepicted). Further, because the direction of the magnetizationorientation 200 exhibited by a strained free region 112 under a verticaltensile stress 600 may depend on the material or materials comprisingthe free region 112, it should be understood that the present disclosureis not limited to achieving a vertical magnetization orientation withinthe free region 112 via a vertical stress that is tensile. In otherembodiments, the materials comprising the free region 112 may be suchthat exerting a vertical compressive stress, directly or indirectly,upon the free region 112 may affect the magnetization orientation withinthe free region 112 so as to effect the desired vertical magnetizationorientation in the strained free region 112. In such embodiments,therefore, the composition of the vertically-adjacent stressorstructures 120V′, 120V″ and the technique for forming thevertically-adjacent stressor structures 120V′, 120V″ may be tailored toachieve vertically-adjacent stressor structures 120V′, 120V″ configuredto exert the vertical compressive stress, directly or indirectly, uponthe free region 112.

In some embodiments, the free region 112 of the cell core 110 mayexhibit a vertically-oriented magnetization orientation 200 even whennot in a strained state, i.e., when not under an externally-exertedstress (e.g., the lateral compressive stress 500, the vertical tensilestress 600, a lateral tensile stress, or a vertical compressive stress).In such embodiments, the stressor structure 120 (e.g.,laterally-adjacent stressor structure(s) 120L, vertically-adjacentstressor structure(s) 120V′, 120V″) according to the present embodimentmay be formulated and configured to maintain the vertical magnetizationorientation exhibited by the strained free region 112.

In other embodiments, the free region 112 of the cell core 110 may beformed in a non-strained state, i.e., not under an externally-exertedstress. The material forming such free region 112 may be formulated toexhibit a vertically-oriented magnetization orientation 200 when, duringuse of the cell core 110, the local temperature of the cell increases.The increase in temperature during use may exert a stress on the freeregion 112 so as to effect a temporary vertically-oriented magnetizationorientation 200. The stress may be caused by thermally-induced expansionof the free region 112, to thermally-induced expansion of one or moreneighboring materials, or to both. For example, during read or write ofthe cell, the local temperature may increase, exerting the stress uponthe free region 112 such that it will be in a strained state and exhibita vertically-oriented magnetization orientation 200. Following use ofthe cell, the local temperature may decrease, relieving the stress, andtransitioning the free region 112 back to the non-strained state. In thenon-strained state, the free region 112 may no longer exhibit thevertically-oriented magnetization orientation 200. Such embodiments maynot include a stressor structure 120. Thus, the stress exerted on thefree region 112 may be either permanent or temporary and may be one ormore of a mechanical stress and a thermal stress.

Also disclosed is a semiconductor device structure including at leastone STT-MRAM cell, e.g., an array of STT-MRAM cells. With reference toFIG. 7, illustrated is a simplified block diagram of a semiconductordevice structure 700 implemented according to one or more embodimentsdescribed herein. The semiconductor device structure 700 includes amemory array 702 and a control logic component 704. The memory array 702may include a plurality of any of the STT-MRAM cells 100 depicted inFIG. 2A through FIG. 4F. The control logic component 704 may beconfigured to operatively interact with the memory array 702 so as toread from or write to any or all memory cells (e.g., STT-MRAM cell 100)within the memory array 702.

Also disclosed is a system including a memory array, e.g., memory array702. With reference to FIG. 8, depicted is a processor-based system 800.The processor-based system 800 may include various electronic devicesmanufactured in accordance with embodiments of the present disclosure.The processor-based system 800 may be any of a variety of types such asa computer, pager, cellular phone, personal organizer, control circuit,or other electronic device. The processor-based system 800 may includeone or more processors 802, such as a microprocessor, to control theprocessing of system functions and requests in the processor-basedsystem 800. The processor 802 and other subcomponents of theprocessor-based system 800 may include magnetic memory devicesmanufactured in accordance with embodiments of the present disclosure.

The processor-based system 800 may include a power supply 804. Forexample, if the processor-based system 800 is a portable system, thepower supply 804 may include one or more of a fuel cell, a powerscavenging device, permanent batteries, replaceable batteries, andrechargeable batteries. The power supply 804 may also include an ACadapter; therefore, the processor-based system 800 may be plugged into awall outlet, for example. The power supply 804 may also include a DCadapter such that the processor-based system 800 may be plugged into avehicle cigarette lighter, for example.

Various other devices may be coupled to the processor 802 depending onthe functions that the processor-based system 800 performs. For example,a user interface 806 may be coupled to the processor 802. The userinterface 806 may include input devices such as buttons, switches, akeyboard, a light pen, a mouse, a digitizer and stylus, a touch screen,a voice recognition system, a microphone, or a combination thereof Adisplay 808 may also be coupled to the processor 802. The display 808may include an LCD display, an SED display, a CRT display, a DLPdisplay, a plasma display, an OLED display, an LED display, athree-dimensional projection, an audio display, or a combinationthereof. Furthermore, an RF sub-system/baseband processor 810 may alsobe coupled to the processor 802. The RF sub-system/baseband processor810 may include an antenna that is coupled to an RF receiver and to anRF transmitter (not shown). A communication port 812, or more than onecommunication port 812, may also be coupled to the processor 802. Thecommunication port 812 may be adapted to be coupled to one or moreperipheral devices 814, such as a modem, a printer, a computer, ascanner, a camera, or to a network, such as a local area network, remotearea network, intranet, or the Internet, for example.

The processor 802 may control the processor-based system 800 byimplementing software programs stored in the memory. The softwareprograms may include an operating system, database software, draftingsoftware, word processing software, media editing software, or mediaplaying software, for example. The memory is operably coupled to theprocessor 802 to store and facilitate execution of various programs. Forexample, the processor 802 may be coupled to system memory 816, whichmay include one or more of spin torque transfer magnetic random accessmemory (STT-MRAM), magnetic random access memory (MRAM), dynamic randomaccess memory (DRAM), static random access memory (SRAM), and otherknown memory types. The system memory 816 may include volatile memory,non-volatile memory, or a combination thereof. The system memory 816 istypically large so that it can store dynamically loaded applications anddata. In some embodiments, the system memory 816 may includesemiconductor device structures, such as the semiconductor devicestructures 700 of FIG. 7, memory cells such as the STT-MRAM cells 100 ofany of FIGS. 2A through 4F, or both.

The processor 802 may also be coupled to non-volatile memory 818, whichis not to suggest that system memory 816 is necessarily volatile. Thenon-volatile memory 818 may include one or more of STT-MRAM, MRAM,read-only memory (ROM) such as an EPROM, resistive read-only memory(RROM), and flash memory to be used in conjunction with the systemmemory 816. The size of the ROM is typically selected to be just largeenough to store any necessary operating system, application programs,and fixed data. Additionally, the non-volatile memory 818 may include ahigh capacity memory such as disk drive memory, such as a hybrid-driveincluding resistive memory or other types of non-volatile solid-statememory, for example. The non-volatile memory 818 may include STT-MRAMdevices formed in accordance with embodiments of the present disclosure,such as semiconductor device structures 700 of FIG. 7, memory cells suchas the STT-MRAM cells 100 of any of FIGS. 2A through 4F, or both.

Accordingly, a memory cell is disclosed. The memory cell comprises amagnetic cell core comprising a free region exhibiting strain effectinga vertical magnetization orientation.

Also disclosed is a memory cell comprising a cell core. The cell corecomprises a free region in a strained state exhibiting a verticalmagnetization orientation. The cell core also comprises a pinned regionand another region disposed between the free region and the pinnedregion.

Further disclosed is a method of forming a memory cell, the methodcomprising forming a cell core and applying a stress to the cell core toaffect a magnetization orientation exhibited by a material within thecell core.

Still further disclosed is a semiconductor device structure comprising aspin torque transfer magnetic random access memory (STT-MRAM) arraycomprising a plurality of STT-MRAM cells. Each STT-MRAM cell of theplurality comprises a cell core comprising a strained free regionexhibiting a vertical magnetization orientation. Each cell alsocomprises a stressor structure external to the cell core. The stressorstructure stresses the strained free region.

Moreover, disclosed is a system comprising a memory array comprising aplurality of magnetic memory cells. Each magnetic memory cell of theplurality comprises at least one stressor structure applying a stress toa free region demonstrating a vertical magnetization orientation.

While the present disclosure is susceptible to various modifications andalternative forms in implementation thereof, specific embodiments havebeen shown by way of example in the drawings and have been described indetail herein. However, the present disclosure is not intended to belimited to the particular forms disclosed. Rather, the presentdisclosure encompasses all modifications, combinations, equivalents,variations, and alternatives falling within the scope of the presentdisclosure as defined by the following appended claims and their legalequivalents.

What is claimed is:
 1. A memory cell, comprising: a magnetic cell coredisposed between a conductive material above the magnetic cell core andanother conductive material below the magnetic cell core, the magneticcell core comprising a five region exhibiting strain effecting avertical magnetization orientation; and at least one stressor structureexternal to the magnetic cell core and applying stress to the magneticcell core, the at least one stressor structure at least partiallyoverlapped by the conductive material above and at least partiallyoverlapping the another conductive material below, the at least onestressor structure physically isolated from each of the magnetic cellcore, the conductive material, and the another conductive material by aninsulative material.
 2. The memory cell of claim 1, wherein the magneticcell core further comprises a pinned region comprising a verticalmagnetization orientation.
 3. The memory cell of claim 1, wherein the atleast one stressor structure exerts at least one of a lateral stress anda vertical stress upon the free region.
 4. The memory cell of claim 1,wherein the at least one stressor structure exerts at least one of acompressive stress and a tensile stress upon the free region.
 5. Thememory cell of claim 1, wherein the magnetic cell core furthercomprises: a pinned region; and a non-magnetic region disposed betweenthe free region and the pinned region.
 6. The memory cell of claim 1,wherein the free region comprises a material exhibitingmagnetostriction.
 7. The memory cell of claim 1, wherein the free regioncomprises a Heusler alloy.
 8. A memory cell, comprising: a cell corevertically between a conductive material and another conductivematerial, the cell core comprising: a free region in a strained stateexhibiting a vertical magnetization orientation; a pinned region; andanother region disposed between the free region and the pinned region;and at least one stressor structure spanning directly between theconductive material and the another conductive material and defining awidth less than or equal to a width of the conductive material and theanother conductive material, the conductive material and the anotherconductive material extending laterally to or past a periphery of the atleast one stressor structure, the at least one stressor structureexerting a stress upon the free region to effect the strained statethereof.
 9. The memory cell of claim 8, wherein a stressor structure, ofthe at least one stressor structure, comprises a stressor materialdisposed between another stressor material and the cell core.
 10. Thememory cell of claim 8, wherein the at least one stressor structurelaterally surrounds the cell core.
 11. The memory cell of claim 8,wherein the cell core is disposed laterally between at least twosegments of the at least one stressor structure.
 12. The memory cell ofclaim 11, wherein the at least one stressor structure applies a lateralcompressive stress to the free region.
 13. The memory cell of claim 8,wherein the cell core is disposed vertically between at least twosegments of at least one other stressor structure.
 14. The memory cellof claim 13, wherein the at least one other stressor structure applies avertical tensile stress to the free region.
 15. A method of forming amemory cell, the method comprising: forming a cell core over aconductive material; forming another conductive material over the cellcore; forming at least one stressor structure vertically above theconductive material and within an insulative material isolating the atleast one stressor structure from the conductive material, the anotherconductive material, and the cell core, the conductive material and theanother conductive material each at least partially overlapping orunderlapping the at least one stressor structure; and applying a stressto the cell core with the at least one stressor structure to affect amagnetization orientation exhibited by a material within the cell core.16. The method of claim 15, wherein forming a cell core comprises:forming a pinned region; forming a non-magnetic region over the pinnedregion; and forming a free region over the non-magnetic region.
 17. Themethod of claim 15, further comprising forming at least one otherstressor structure on the cell core, the at least one other stressorstructure comprising a stressor material having a coefficient of thermalexpansion differing from a coefficient of thermal expansion of aneighboring material of the cell core.
 18. The method of claim 17,further comprising, following forming the at least one other stressorstructure, reducing a temperature of the at least one other stressorstructure to stress the neighboring material and affect themagnetization orientation of a free region within the cell core.
 19. Asemiconductor device structure, comprising: a spin torque transfermagnetic random access memory (STT-MRAM) array comprising: a pluralityof STT-MRAM cells, each STT-MRAM cell of the plurality comprising: acell core comprising a strained free region exhibiting a verticalmagnetization orientation; and at least one stressor structure externalto the cell core and extending essentially only a height of the freeregion, the at least one stressor structure stressing the strained freeregion.
 20. The semiconductor device structure of claim 19, wherein theat least one stressor structure spans between the free region of oneSTT-MRAM cell of the plurality and another free region of anotherSTT-MRAM cell of the plurality.
 21. A spin torque transfer magneticrandom access memory (STT-MRAM) cell, comprising: a magnetic cell corecomprising a free region; a word line in operable communication with thecell core; a bit line in operable communication with the cell core; thefree region exhibiting a strain effecting a magnetization orientationdirected toward one of the word line and the bit line; and at least onestressor structure contacting the word line and the bit line anddisposed laterally between the magnetic cell core and an insulativematerial, a periphery of the at least one stressor structure defining awidth equal to or less than a width defined by the word line and a widthdefined by the bit line.